How to reset TCP/IP and Winsock under Windows 8 ?

To reset TCP/IP in Windows, use either elevated(admin) Command Prompt, or the Windows PowerShell. Both can be accessed by searching the Start menu, right-click and choose to "Run as administrator" to have sufficient permissions to make changes.

To reset TCP/IP:

netsh int ip reset
alternative syntax: netsh int ipv4 reset

Note that under Windows 8.x, the netsh command is deprecated and not always works. You may see the following error when trying to use netsh to reset TCP/IP:
Resetting , failed.
Access is denied.

In such cases, to reset TCP/IP, try the following PowerShell cmdlet instead:

Remove-NetIPAddress

To reset Winsock under Windows 8/8.1 the netsh command still works (under elevated command prompt, or Admin PowerShell):

netsh winsock reset

Note: It's been suggested that the "netsh int ip reset" command fails because of insufficient permissions in the following registry key on some systems: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nsi\{eb004a00-9b1a-11d4-9123-0050047759bc}\26 (right-click on the key in regedit -> permissions -> tick "full control")